Practical method validation: Validation sufficient for an analysis method

Validation of an analysis method depends on the purpose of the method, the chosen technique and the procedure in question. Methods are used for different research, product development, process control and quality control purposes. The human and economical importance of results vary. Each of the techniques used, such as chromatography-(HPLC, HRGC, TLC), capillary electrophoresis-(CE), spectrophotometry-(UV/VIS, IR, fluorescence, AAS, ICP) or spectrometric techniques (NMR, MS) as well as the hyphenated methods, have their own special features and deficiencies which must be considered. The method can include a simple pretreatment or it may include many demanding steps, it can use automation and data processing in various ways, it can have an official status, it can be a thoroughly verified or less studied one. How should these differences be accounted for during the validation? What would be a sufficient certainty that the method does what is expected, that the method fits for the purpose it was intended?